Plural speed data receiver



R. L. FRANK PLURAL SPEED DATA RECEIVER Jan. ze, 1960 Filed Abril 9, 1957 ATTORNEY States Pafit 2,922,991 PLURAL SPEED DATA RECEIVER Robert L. Frank, Great Neck, N.Y., assignor to Sperry Rand Corporation, a corporation of Delaware Application April 9, 1957, Serial No. 651,671 6 claims. (c1. 340-181) 2,922,991" ce f Patented Jan. 26, 1960,

a plural speed data receiver, to reduce the dynamic lag of the coarser data indicators to that of the most precise data indicator.

Another object of the present invention is to maintain the dynamic response characteristic of a plural speed data receiver despite the introduction of means to render ticularly, to means for enhancing the dynamic response i of such receivers under conditions of high rate of change of data.

Datatransmission systems are well known in the art for causing, for example, a plurality of driven shafts at the data receiver to be positioned in accordance with the l displacements of a control shaft at the data transmitter.

'Ifhe receivers for use in such data transmission systems incorporate more than one data follower such as a servomechanism, each servomechanism driving a respective shaft-at different but predetermined rates of speed, the position of the lowest speed shaft corresponding to coarse data while the position of the highest speed shaft corresponds to line data. The .function'of the coarse data is toremove theambiguity inherent in the fine data as reproduced by the data receiver.

` -For example, as in a well known 36:1 dual speed transmission system, each single complete rotation of the control shaft at the transmitter will produce one complete revolution of the coarse shaft and thirty-six complete revolutions of the tine shaft at the receiver. In a the receiver coarser data reproducers less susceptible to the presence of noise.

An additional object of the present invention is to provide a dual speed data receiver wherein the coarse data indicator is jointly driven by coarse and fine servomechanisms and wherein the fine data indicator is solely driven by the ne servomechanism.

Yet another object of the present invention is to provide a dual speed data receiver wherein the coarse indicator is solely driven by a coarse servomechanism under static data conditions but wherein the coarse indicator is jointly driven by the coarse and a line servomechanism under dynamic data conditions.

These and other objects of the present invention, as

will appear from the following description, are accomnism. Dilerential means are provided for .driving the manner analogous to the fashion in which the minute in order to produce a final reading having the precision of the fine shaft displacement but having the ambiguity resolution property of the coarse shaft.

Each of the coarse and fine receiver data reproducers are in themselves independent devices and are commonly of the null-seeking'type. Inasmuch as a predetermined plurality of rotations of the fine shaft correspond to a single rotation of the coarse shaft, the gradient of the coarse error signal about its null is low relative to the gradient of the fine error signal about its corresponding null.' It is because of this difference in error gradients that 4the coarse servomechanism inherently suifers the following two disadvantages not shared to the same degree by the fine servomechanism: (l) dynamic response, i.e., the ability tofollow changing data, is less; and (2) susceptibility to random variations in the coarse data signal is greater, whereby erroneous coarse data indications may result.

l One of the techniques employed in the art for minimizing the undesirable susceptibility of the coarse servomechanism to noise (i.e., random variations in the coarse data signal) is to introduce integrating or filtering means in the coarse servomechanism error signal channel where# coarse indicator jointly by means of the coarse and tine servomechanisms. The total data is read by combining the coarse and line data indications. i For a morel complete understanding of the present invention, reference should be had to the following description and the appended drawings of which Fig. l is an illustrative dual speed data transmission system embodiment of the present invention wherein data is transmitted in the form of the phase ofcoarse and ne control signals; and

Fig. 2 is a diagram of superimposed error signal characteristics of coarse and fine data receiver servomechanisms of the null-seeking type such as shown in Fig. 1.

In Fig. 1, a data source for a dual speed data transmission system is generally represented by the numeral 1. By way of example, the system of Fig. 1 is arbitrarily chosen to be of a phase sensitive type wherein data is communicated in form of the phase of coarse and fine control signals. Accordingly, the components contained within data source 1 are arranged to provide three A C. output signals, appearing on conductors 2, 3, and 4, which are utilized in different pairs, respectively, by the coarse and fine servomechanisms 36 and 35 embodied in the receiver portion of the apparatus of Fig. 1.

Oscillator 27 produces a signal at a convenient frequency for application to the electrical inputs of phase Shifters 29, 30, 6 and 20. Phase Shifters 29, 30, 6 and 20 each may be in the form of a resolver and phase shifting network having an electrical input and providing an electrical output whose phase, relative to that of the input, is determined by a function of the angular displacement of its resolver rotor. The rotor of phase shifter 29 is manually positionable by means of shaft 31, which shaft is also coupled to the input of gearing 32. Gearing 32 produces a predetermined ratio between the v mechanical displacements of its input and output shafts which establishes the relationship between the periodicity of the coarse and fine data signals as is well known in the art. The output of gearing 32 mechanically displaces the rotor of phase shifter 30 by means of shaft 33. Thus, there is produced on line 2 and alternating signal at the frequency of oscillator 27 having a phase relative thereto asdetermined by a function of the angular displacement of shaft 31. Similarly, there is produced on line 3 a signal at the same frequency as that of oscillator 27 but having a phase'relative'thereto as determined by' plied to a first input of phase detectorS whose second input is derived from the output of phase shifter 6 via 1ine13. In a well known manner, phase detector `5, which is assumed to contain low pass filtering; means, will produce at its output a D.C. signal whose amplitude is proportional to the cosine of the phase angle' between the signals applied via lines 13 and 2j. The resultant' DrC.' signal, appearing on line 7', is. ampliied'nas by` amplifier 8: and applied. to D.C; motor 10 via low passjvlilter 9,` the purpose of which will appear later.; DQ. motor 10 will rotate at a speed determined by the amplitude' Yof,

the. applied D'.C.Verror'signal and in a direction' deter-1 mined by the polarity thereof.` Motor'ltl drivesshaft 11 which in turn positions. the rotor 15 'of phase shifter 6 by means of differential 12.V The displacement of shaft 15 of phase shifter 6 is indicated by coarse indicator 16. The Vine control. signal, appearing on line 3,V is applied to a iirst input of phase detector'17, which mayV take Vthe same form as phase detector 5. The Vsecondinput of phase detector 17 is derived from the output of phase shifter 20 via line 14. In a fashion similar to that described in connection with the coarse servomechanism, phase detector 17 Willproduce a kD.C. output having an amplitude proportional to the cosine of the phase angle between the signals appearing on lines 3` and 14 andh'av-A ing a polarity determined by. thequadi'ant in which said` angle lies.A The resultant D.C, error signal is amplified by amplifier 18 'and applied to D.C'. motor 1.9 whose shaft 22 positions the rotor of phase shifter 2l). The displacement of shaft 22 is shown on fine indicator 21;.

In operation, the rotor of phase shifter tisdriven to such a position by motor 10 that the phase ofthe signal appearing on line I3 is placedin quadrature with the phase of the signal appearingy on line. 2. As is well known, when such aphase relationship exists at the inputs toa phase detector, a zero output signal will' be produced. Thus, the coarse servomechanism vi's of aV null-seeking type. The operation ofthe ine servomechanism precisely parall'els this. i

The apparatus 'so far described willY function asfallows. For a given angular displacement of input control shaft 31, output shaft 15 of coarse servomechanism'Y 36 will be displaced an. equal number off degrees. The cor.- responding displacement of output shaft22. of -nefservomechanism 35 will be a multiple. of the angular displacement'of control shaft 31 as determined by the ratio produced by gearing 32. Assuming that a fixed. displacement is imparted to input control shaft 31, coarse shaft 15 and ine shaft 22 will ultimately assume rest positions which will be displayed in appropriateunits by the respective indicators 16 and Z1. In a4 fashion directly analogous` to the manner in which time is-V determined by combining the indications produced by the hour. and minute hands of a clock, the positionof inputshaftf 31 isfascertained by combining the presentationsof indicators 1'6' and 21.

Fig, 2 illustrates the superimposed Verror signal characteristics of coarse and` fine servomechanisms such as signal ils required to produce a predetermined rate of rotation of said motors. It can be seen that because of the difference in error signal gradients'about their corresponding nulls, the coarse servomechanism must lag the n iine servomechanism in order to produce the same amplitude of error signal. In other words, under conditions of rate of change of input data (correspondingA to con tinued rotation of input shaft 31), indicator 16 will tend to lag indicator" 21.V

The present invention. substantially eliminates the rela-` tive lag ofthe coarse`data indicator in the dyrri inode of operation by the addition of gearing 23 and differential 12 to the structure of Fig'. 1 previously" described'. Referring to Fig. l., gearing 23 producesthe same ratio as that produced bygearing 32 between its input shaft 34 and'its output shaft 24. Input shaft 34 is driven by shaft 22 of motorY 19 while output shaft 24 is applied to a second input of dilerential 12Awhosefirst input, as previously described, is obtainedl from shaft '11`.V Thus,

coarse indicator 16 is connected jointly to rfine"siejrfof mechanism shaft 22v (via gearing 23) and coarse servomechanism shaftY 11, whereas line indicator 21 is connected solely to iine servomechanism shaft 22. The displacement ratio produced by gearing. 23 serves to transformA or reference the displacement of fine` s`haft, 22 in terms of the displacement ofl coarse shaftfll for any given movement of input shaft-31. n y Y l d It will be observed, however, that under. dynamic data conditions, coarseV indicator 16V will `be drivenV solely by fine servomechanism shaft 22.l As previouslyV discussed, shaft 22 will follow changes in the'v position of sha-ftlmore rapidly than will shaft 11. For thisl reason, whatf e; ever changes are necessary inthe Vdisplacement of shaft 15`of` phase shifter 6, so asl to maintain ap'quadraturegphase relationship between the signals appearing on lines 13 and Z, will be imparted by the faster responding.' shaft 22. YIn other words, output shaft 1'1- of the coarse `servomecha- A nism will remain at' rest during.. the application of a changing displacement of` shaft 31. As previously mentioned, the relatively low error 1Sig-` A nalA gradient about the null of the coarse servo, in addi-l tion to giving rise to a lag under dynamic data conditions, will also render the coarse servo more susceptible to noise. Low pass filter 9 has been insertedin the error signal path of coarse servo 36 as a means for averaging out random fluctuations attributable tov noise. It should be observed, however, that the improvedresponse ofthe coarse servo 36,` accomplishedbyfthe. differential Vcoarse and tine servo drive ofvshaft 15, is notadversely/aifencted thereby. lnasmuch as shaft 15W is driven substantially alone by the line servo under dynamic data'conditions, the amount of filtering introduced inthe coarse servo' error. signalpath doesnot inliuence-the dynamic response ofthe. coarse servo. f Y A Although coarse indicator 16- is drivenwith the dynamic precision of fine servomechanism shaft 22 the datadisplayed by lineA indicator 21 is neverthelessvindispensable inorder to produce atotal'readinghaving highshown in Pig. 2. A 5:1, coarse-to-iine ratio is used.Y as t anexample. Upon examination` of Fig.V 2, itcanbeseen that for a given'qdeviation fromtheir respectivenulls,- the amplitude of the line error signal` Willbe much.. greater than theA correspondingV amplitude. of? the.coarse. error f signal. klnasmuch as motors liand. 19'. must drive.pre

determined loads presented by friction and.' mechanical icrtlmfor example,, a.predeterminediamplitude,pierro;

est precision. This. is. so because any quiescent static error in the positionY of coarse servomechanismv shaft-11 n fine. data indicators.y Accordingto the,y present. invention;

the tine data indicatorrisgdrivenisolely` bytheiinerservog mechanism v whereas the/coarse.V data-indicator is jointly driven thereby. The total data receivedisreadvby 'conif binngnhe coarseand neindications.. V-

It will be observed that although mechanical summing means, such as differential 12, is shown in the illustrative embodiment of Fig. l, the invention also contemplates the electrical summation of the coarse and fine data signals for purposes of jointly controlling a single driven device particularly in cases wherein the coarse and tine data signals, as reproduced by the data receiver, are in the form of electrical signals rather than mechanical signals as shown in Fig. l.

Moreover, the present invention is not limited to application to coarse and fine data receivers of a phase measuring type but is readily adaptable to other conventional types such as are responsive to other characteristics of input data signals such as, for example, to the amplitude and polarity of electrical signals.

Additionally, it will be clear that the present invention is readily applicable to multi-speed communication receivers wherein one or more of the coarser data indicators are individually driven by the combined output of a respective coarser data servo and the output of the finest data servo.

While the invention has been described in its preferred embodiments, it is to be understood that the Words which have been used are words of description rather than of limitation and that changes within the purview of the appended claims may be made without departing from the true scope and spirit of the invention in its broader aspects.

What is claimed is:

l. In a plural speed data receiver, first and second means adapted to receive data in the form of respective input signals having a common characteristic and operative to reproduce said data in the form of first and second output signals, said characteristic of one of said respective input signals bearing a predetermined relationship with respect to the same characteristic of the other of said respective input signals, means for referencing said first output signal to said second output signal in accordance with said predetermined relationship, and signal summing means having two inputs, said first output signal being applied to said first input by said means for referencing, and said second output signal being applied to said second input.

2. 1n a plural speed data receiver, first and second means each adapted to receive data in the form of respective input signals having a common characteristic and operative to reproduce said data in the form of rst and second output signals, said characteristic of one of said respective input signals bearing a predetermined relationship with respect to the same characteristic of the other of said respective input signals, first and second utilization means adapted to' respond to a respective one of said output signals, means for applying said first output signal to said first utilization means, means for referencing said first output signal to said second output signal in accordance with said predetermined relationship, signal summing means having two inputs and an output, said first output signal being applied to said first input by said means for referencing, said second output signal being applied to said second input, and means connecting the output of said summing means to said second utilization means.

of said respective input signals by a predetermined ratio greater than unity, said servo means being adapted to reproduce said data in the form of first and second output signals, rst and second utilization means adapted to respond to a respective one of said output signals, means for applying said first output signal to said first utilization means, means for referencing said first output signal to said second output signal in accordance with said predetermined ratio, signal summing means having two inputs and an output, said first output signal being applied to said first input by said means for referencing, said second output signal being applied to said second input, and means for connecting said output to said second utilization means.

4. In combination, first and second phase-sensitive servo means, each adapted to receive a respective control signal having an adjustable phase relative to the phase of a corresponding reference signal of the same frequency, the rate of change of phase of the control signals being mutually related by a predetermined ratio, said servo means producing respective output signals having a. characteristic proportional to the phase difference between a corresponding control signal and its respective reference signal, means for referencing said first output signal to said second output signal in accordance with said predetermined ratio, and signal summing means having two inputs, said first output signal being applied to said first input by said means for referencing, said second output signal being applied to said second input.

5. In combination, first and second phase-sensitive servo means, each adapted to receive a respective control signal having an adjustable phase relative to the phase of a corresponding reference signal of the same frequency, the rate of change of phase of the control signals being mutually related by a predetermined ratio, each said servo means producing an output signal in the form of the displacements of a respective shaft, the displacement of each shaft being proportional to the phase difference between a corresponding control signal and its respective reference signal, signal summing means having two inputs, and gearing means for connecting one of the shafts to said first input, the other of the shafts being connected to said second input.

6. In combination, first and second phase-sensitive servo means, each adapted to receive a respective control signal having an adjustable phase relative to the phase of a corresponding reference signal of the same frequency, the rate of change of phase of the control signals being mutually related by a predetermined ratio, each said servo means producing an output signal in the Y form of the displacements of a respective shaft, the dis- 3. In a plural speed data receiver, first and second I 'same qualitative but different quantitative nature, the

characteristic of one of said respective input signals being related quantitatively to said characteristic `of the other placement of each shaft being proportional to the phase difference between a corresponding control signal and its respective reference signal, first and second utilization means adapted to respond to respective ones of the shafts, means for connecting one of the shafts to said first utilization means, mechanical differential means having two inputs and an output, gearing means for connecting said one of the shafts to said first input, the other of the shafts being connected to said second input, and

lmeans for coupling the output of said differential means to said second utilization means.

References Cited the file of this patent UNITED STATES PATENTS 2,670,456 Naylor Feb. 23, 1954 2,719,940 West Oct. 4, 1955 2,735,971 Roven et al. Feb. 21, 1956 

